7 Mutations and Genetic Variation Free Online FlashCards

What is a mutation?

A mutation is a lasting change in the DNA sequence.

How does a DNA lesion differ from a mutation?

A DNA lesion is damage. It becomes a mutation if it is copied or repaired in a way that permanently changes the sequence.

What are two spontaneous sources of mutations?

Replication errors and spontaneous chemical changes, such as oxidation or deamination of DNA bases, can cause mutations.

How can UV and ionizing radiation damage DNA?

Mutagens can damage DNA: UV radiation can create pyrimidine dimers, while ionizing radiation can damage bases or break DNA strands.

How does inheritance differ for germ-cell and somatic mutations?

A germ-cell mutation may be passed to offspring. A somatic-cell mutation affects that cell and its descendants but is generally not inherited by offspring.

What are the three possible effects of a coding-sequence substitution?

A substitution replaces one nucleotide. It is silent if the amino acid stays the same, missense if it changes, and nonsense if the codon becomes a stop.

When does an insertion or deletion cause a frameshift?

An insertion or deletion not in a multiple of three shifts the reading frame, altering downstream codons and often introducing an early stop.

What is the effect of an in-frame insertion or deletion?

An insertion or deletion in a multiple of three adds or removes amino acids without shifting the reading frame.

What can larger-scale mutations affect?

Mutations can affect parts of genes, whole genes, or broader chromosome regions through deletions, duplications, or rearrangements.

Why can the same DNA change have different effects?

A mutation’s effect depends on where it occurs and its biological context. It may alter a protein’s function or change when or how much RNA is produced.

How does mismatch repair correct replication errors?

Mismatch repair recognizes certain mismatched bases or small insertion–deletion loops left after replication, then replaces part of the new strand using the original as a template.

What does base-excision repair do?

Base-excision repair removes a damaged or chemically altered base, then fills and seals the resulting gap.